kde-extraapps/kdevplatform/language/duchain/duchainpointer.h

/*
   Copyright 2007 David Nolden <david.nolden.kdevelop@art-master.de>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License version 2 as published by the Free Software Foundation.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/

#ifndef KDEVPLATFORM_DUCHAINPOINTER_H
#define KDEVPLATFORM_DUCHAINPOINTER_H

#include <QtCore/QMetaType>
#include <ksharedptr.h>
#include "../languageexport.h"

//krazy:excludeall=dpointer

namespace KDevelop {

class DUContext;
class TopDUContext;
class DUChainBase;
class Declaration;
class AbstractFunctionDeclaration;

/**
 * Whenever the du-chain is unlocked and locked again, any du-chain item may have been deleted in between.
 * For that reason, the following class should be used to make sure that no deleted objects are accessed. It contains a pointer
 * that will be reset to zero once the pointed object is deleted.
 *
 * Access to the data must still be serialized through duchain-locking. Using this comes with no additional cost.
 *
 * In practice this means:
 * Store an instance of DUChainPointer instead of a pointer to the du-chain object.
 * Then, access the eventually still existing object by calling pointer->base().
 *
 * To make it even more convenient see DUChainPointer
 * */

class KDEVPLATFORMLANGUAGE_EXPORT  DUChainPointerData : public QSharedData {
  public:
    /**
     * Will return zero once the pointed-to object was deleted
     * */
    DUChainBase* base();

    /**
     * Will return zero once the pointed-to object was deleted
     * */
    DUChainBase* base() const;

    ///Default-initialization of an invalid reference
    DUChainPointerData();

    ~DUChainPointerData();

  private:
    ///Should not be used from outside, but is needed sometimes to construct an invalid dummy-pointer
    DUChainPointerData( DUChainBase* base );

    friend class DUChainBase;
    DUChainBase * m_base;
    Q_DISABLE_COPY(DUChainPointerData)
};

/**
 * A smart-pointer similar class that conveniently wraps around DUChainPointerData without
 * too many dynamic casts.
 *
 * It can be used like a normal pointer.  In order to cast between pointer types, you should
 * use the staticCast() and dynamicCast() functions as appropriate.
 *
 * Access must be serialized by holding the KDevelop::DUChain::lock() as appropriate for the
 * function(s) being called.
 **/

  template<class Type>
  class DUChainPointer {
    template<class OtherType>
    friend class DUChainPointer;

    public:
    DUChainPointer() : d(KSharedPtr<DUChainPointerData>(0)) {
    }

    DUChainPointer(const DUChainPointer& rhs)
      : d(rhs.d)
    {
    }

    ///This constructor includes dynamic casting. If the object cannot be casted to the type, the constructed DUChainPointer will have value zero.
    template<class OtherType>
    explicit DUChainPointer( OtherType* rhs ) {
      if( dynamic_cast<Type*>(rhs) )
        d = rhs->weakPointer();
    }

    template<class OtherType>
    explicit DUChainPointer( DUChainPointer<OtherType> rhs ) {
      if( dynamic_cast<Type*>(rhs.data()) )
        d = rhs.d;
    }

    explicit DUChainPointer( KSharedPtr<DUChainPointerData> rhs ) {
      if( dynamic_cast<Type*>(rhs->base()) )
        d = rhs;
    }

    explicit DUChainPointer( Type* rhs ) {
      if( rhs )
        d = rhs->weakPointer();
    }

    bool operator ==( const DUChainPointer<Type>& rhs ) const {
      return d.data() == rhs.d.data();
    }

    bool operator !=( const DUChainPointer<Type>& rhs ) const {
      return d.data() != rhs.d.data();
    }

    ///Returns whether the pointed object is still existing
    operator bool() const {
      return d && d->base();
    }

    Type& operator* () const {
      Q_ASSERT(d);
      return *static_cast<Type*>(d->base());
    }

    Type* operator->() const {
      Q_ASSERT(d);
      return static_cast<Type*>(d->base());
    }

    bool operator<(const DUChainPointer<Type>& rhs) const {
      return d.data() < rhs.d.data();
    }

    template<class NewType>
    DUChainPointer<NewType> dynamicCast() const {
      if( dynamic_cast<NewType*>( d->base() ) ) //When the reference to the pointer is constant that doesn't mean that the pointed object needs to be constant
        return DUChainPointer<NewType>( static_cast<NewType*>(d->base()) );
      else
        return DUChainPointer<NewType>();
    }

    Type* data() const {
      if( !d )
        return 0;
      return static_cast<Type*>(d->base());
    }

    DUChainPointer<Type>& operator= ( Type* rhs ) {
      if( rhs )
        d = rhs->weakPointer();
      else
        d = 0;

      return *this;
    }

    private:
      KSharedPtr<DUChainPointerData> d;
  };

  typedef DUChainPointer<DUChainBase> DUChainBasePointer;
  typedef DUChainPointer<DUContext> DUContextPointer;
  typedef DUChainPointer<TopDUContext> TopDUContextPointer;
  typedef DUChainPointer<Declaration> DeclarationPointer;
  typedef DUChainPointer<AbstractFunctionDeclaration> FunctionDeclarationPointer;
}

Q_DECLARE_METATYPE( KDevelop::DUChainBasePointer )
Q_DECLARE_METATYPE( KDevelop::DeclarationPointer )
Q_DECLARE_METATYPE( KDevelop::DUContextPointer )
Q_DECLARE_METATYPE( KDevelop::TopDUContextPointer )
Q_DECLARE_METATYPE( QList<KDevelop::DeclarationPointer> )

#endif